Answer: Hello there!
your set is {(1,-2), (0,4), (2,-3)} where the pairs have the form (x,y)
You want to know with pair you need to add to this set in order to make it "not a function"
The priority rule for a function is the unicity; this means that each value of x has only one value of y associated; or:
if f(x) = y1 and f(x) = y2, then y1 = y2
(notice that a given value of y can be related to different values of x; for example the function f(x) = x^2 has the same y value for x and -x)
Then the problem is if we add the pair (0,2), of option C.
because we already have a pair with the value of x = 0, in the form of (0,4), and these two pairs would have a different value of y for the same value of x, then this set doesn't represent a function anymore.
Then the correct option is C
